Various methods and devices have been employed in shoes to add cushioning to the shoe and to provide complementary custom fitting configurations to the contours of a foot inserted into the shoe. One example is U.S. Pat. No. 5,313,717 to Allen et al. ("Allen"), in which a reactive energy fluid filled cushioning and stabilizing apparatus in a shoe is comprised of one or more anatomically shaped fluid filled bladders that are positioned in the forefoot, arch and/or heel areas of the shoe. As discussed therein, typical prior art devices provide cushioning and custom fit to the foot inside the shoe by constructing the shoe sole from a softer, more resilient material or incorporating fluid filled pads or bladders in the shoe.
The use of gels to provide a conforming fit or cushion is generally known in the prior art. Prior art gels are generally pre-set to fit the contours of a foot or they are soft liquid gels that must be placed in a bladder. Some examples of prior art gels are U.S. Pat. Nos. 5,155,927 and 5,493,792 to Bates, which disclose athletic shoes constructed to minimize impact shock and maximize lateral stability by use of a cushioning element comprising a chamber having flexible walls filled with a liquid composition which is preferably a gel and the chamber has a plurality of partitions for directing the flow of liquid from one portion of the chamber to another.
In other shoes designed to provide cushioning or custom fitting, either an air filled foam or an air bladder has been used to conform to the foot which is inserted into the shoe. The foam is a material that reacts to foot pressure by allowing the air therein to become compressed and/or escape and therefore resiliently compresses upon pressure from the foot. The material does not have the capability to expand to the non-pressure areas of the foot. Shoes that incorporate an air bladder fill in air around the foot so that the shoe conforms to the foot therein, but in doing so, increases the pressure on the foot. This increased pressure and foot surrounding air pocket tends to greatly increase the foot temperature. Thus, these solutions provide fit or comfort either by merely displacing material at locations of higher pressure or by increasing the pressure completely around the foot. Thus, these shoes do not conform fully to the foot therein at normal pressures.
Gels having a liquid to gel transition range are also generally known in the art. For example, U.S. Pat. No. 5,143,731 to Viegas et al. ("Viegas") discloses the use of aqueous pharmaceutical vehicles containing a polyoxyalkylene non-ionic block copolymer, which are liquid at ambient temperatures and transition at mammalian body temperatures to a semi-solid gel by the inclusion of polysaccharide.
The viscosity change at the transition range of prior art gels has not been considered important, which is one reason why such gels have not been commonly utilized as foot conforming components. Most prior art gels are not thermally-responsive. Even in those gels that are temperature-responsive, the viscosity improvement at the transition range is not significant. Thus, there remains a need for improved shoe conforming components and gels for use in such components.